bfd/format.c

   1 /* Generic BFD support for file formats.
   2    Copyright (C) 1990-2021 Free Software Foundation, Inc.
   3    Written by Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22
  23 /*
  24 SECTION
  25         File formats
  26
  27         A format is a BFD concept of high level file contents type. The
  28         formats supported by BFD are:
  29
  30         o <<bfd_object>>
  31
  32         The BFD may contain data, symbols, relocations and debug info.
  33
  34         o <<bfd_archive>>
  35
  36         The BFD contains other BFDs and an optional index.
  37
  38         o <<bfd_core>>
  39
  40         The BFD contains the result of an executable core dump.
  41
  42 SUBSECTION
  43         File format functions
  44 */
  45
  46 #include "sysdep.h"
  47 #include "bfd.h"
  48 #include "libbfd.h"
  49
  50 /* IMPORT from targets.c.  */
  51 extern const size_t _bfd_target_vector_entries;
  52
  53 /*
  54 FUNCTION
  55         bfd_check_format
  56
  57 SYNOPSIS
  58         bool bfd_check_format (bfd *abfd, bfd_format format);
  59
  60 DESCRIPTION
  61         Verify if the file attached to the BFD @var{abfd} is compatible
  62         with the format @var{format} (i.e., one of <<bfd_object>>,
  63         <<bfd_archive>> or <<bfd_core>>).
  64
  65         If the BFD has been set to a specific target before the
  66         call, only the named target and format combination is
  67         checked. If the target has not been set, or has been set to
  68         <<default>>, then all the known target backends is
  69         interrogated to determine a match.  If the default target
  70         matches, it is used.  If not, exactly one target must recognize
  71         the file, or an error results.
  72
  73         The function returns <<TRUE>> on success, otherwise <<FALSE>>
  74         with one of the following error codes:
  75
  76         o <<bfd_error_invalid_operation>> -
  77         if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
  78         <<bfd_core>>.
  79
  80         o <<bfd_error_system_call>> -
  81         if an error occured during a read - even some file mismatches
  82         can cause bfd_error_system_calls.
  83
  84         o <<file_not_recognised>> -
  85         none of the backends recognised the file format.
  86
  87         o <<bfd_error_file_ambiguously_recognized>> -
  88         more than one backend recognised the file format.
  89 */
  90
  91 bool
  92 bfd_check_format (bfd *abfd, bfd_format format)
  93 {
  94   return bfd_check_format_matches (abfd, format, NULL);
  95 }
  96
  97 struct bfd_preserve
  98 {
  99   void *marker;
 100   void *tdata;
 101   flagword flags;
 102   const struct bfd_arch_info *arch_info;
 103   struct bfd_section *sections;
 104   struct bfd_section *section_last;
 105   unsigned int section_count;
 106   unsigned int section_id;
 107   struct bfd_hash_table section_htab;
 108   const struct bfd_build_id *build_id;
 109   bfd_cleanup cleanup;
 110 };
 111
 112 /* When testing an object for compatibility with a particular target
 113    back-end, the back-end object_p function needs to set up certain
 114    fields in the bfd on successfully recognizing the object.  This
 115    typically happens in a piecemeal fashion, with failures possible at
 116    many points.  On failure, the bfd is supposed to be restored to its
 117    initial state, which is virtually impossible.  However, restoring a
 118    subset of the bfd state works in practice.  This function stores
 119    the subset.  */
 120
 121 static bool
 122 bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve,
 123                    bfd_cleanup cleanup)
 124 {
 125   preserve->tdata = abfd->tdata.any;
 126   preserve->arch_info = abfd->arch_info;
 127   preserve->flags = abfd->flags;
 128   preserve->sections = abfd->sections;
 129   preserve->section_last = abfd->section_last;
 130   preserve->section_count = abfd->section_count;
 131   preserve->section_id = _bfd_section_id;
 132   preserve->section_htab = abfd->section_htab;
 133   preserve->marker = bfd_alloc (abfd, 1);
 134   preserve->build_id = abfd->build_id;
 135   preserve->cleanup = cleanup;
 136   if (preserve->marker == NULL)
 137     return false;
 138
 139   return bfd_hash_table_init (&abfd->section_htab, bfd_section_hash_newfunc,
 140                               sizeof (struct section_hash_entry));
 141 }
 142
 143 /* Clear out a subset of BFD state.  */
 144
 145 static void
 146 bfd_reinit (bfd *abfd, unsigned int section_id, bfd_cleanup cleanup)
 147 {
 148   _bfd_section_id = section_id;
 149   if (cleanup)
 150     cleanup (abfd);
 151   abfd->tdata.any = NULL;
 152   abfd->arch_info = &bfd_default_arch_struct;
 153   abfd->flags &= BFD_FLAGS_SAVED;
 154   abfd->build_id = NULL;
 155   bfd_section_list_clear (abfd);
 156 }
 157
 158 /* Restores bfd state saved by bfd_preserve_save.  */
 159
 160 static bfd_cleanup
 161 bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
 162 {
 163   bfd_hash_table_free (&abfd->section_htab);
 164
 165   abfd->tdata.any = preserve->tdata;
 166   abfd->arch_info = preserve->arch_info;
 167   abfd->flags = preserve->flags;
 168   abfd->section_htab = preserve->section_htab;
 169   abfd->sections = preserve->sections;
 170   abfd->section_last = preserve->section_last;
 171   abfd->section_count = preserve->section_count;
 172   _bfd_section_id = preserve->section_id;
 173   abfd->build_id = preserve->build_id;
 174
 175   /* bfd_release frees all memory more recently bfd_alloc'd than
 176      its arg, as well as its arg.  */
 177   bfd_release (abfd, preserve->marker);
 178   preserve->marker = NULL;
 179   return preserve->cleanup;
 180 }
 181
 182 /* Called when the bfd state saved by bfd_preserve_save is no longer
 183    needed.  */
 184
 185 static void
 186 bfd_preserve_finish (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_preserve *preserve)
 187 {
 188   if (preserve->cleanup)
 189     {
 190       /* Run the cleanup, assuming that all it will need is the
 191          tdata at the time the cleanup was returned.  */
 192       void *tdata = abfd->tdata.any;
 193       abfd->tdata.any = preserve->tdata;
 194       preserve->cleanup (abfd);
 195       abfd->tdata.any = tdata;
 196     }
 197   /* It would be nice to be able to free more memory here, eg. old
 198      tdata, but that's not possible since these blocks are sitting
 199      inside bfd_alloc'd memory.  The section hash is on a separate
 200      objalloc.  */
 201   bfd_hash_table_free (&preserve->section_htab);
 202   preserve->marker = NULL;
 203 }
 204
 205 /*
 206 FUNCTION
 207         bfd_check_format_matches
 208
 209 SYNOPSIS
 210         bool bfd_check_format_matches
 211           (bfd *abfd, bfd_format format, char ***matching);
 212
 213 DESCRIPTION
 214         Like <<bfd_check_format>>, except when it returns FALSE with
 215         <<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>.  In that
 216         case, if @var{matching} is not NULL, it will be filled in with
 217         a NULL-terminated list of the names of the formats that matched,
 218         allocated with <<malloc>>.
 219         Then the user may choose a format and try again.
 220
 221         When done with the list that @var{matching} points to, the caller
 222         should free it.
 223 */
 224
 225 bool
 226 bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
 227 {
 228   extern const bfd_target binary_vec;
 229 #if BFD_SUPPORTS_PLUGINS
 230   extern const bfd_target plugin_vec;
 231 #endif
 232   const bfd_target * const *target;
 233   const bfd_target **matching_vector = NULL;
 234   const bfd_target *save_targ, *right_targ, *ar_right_targ, *match_targ;
 235   int match_count, best_count, best_match;
 236   int ar_match_index;
 237   unsigned int initial_section_id = _bfd_section_id;
 238   struct bfd_preserve preserve, preserve_match;
 239   bfd_cleanup cleanup = NULL;
 240
 241   if (matching != NULL)
 242     *matching = NULL;
 243
 244   if (!bfd_read_p (abfd)
 245       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 246     {
 247       bfd_set_error (bfd_error_invalid_operation);
 248       return false;
 249     }
 250
 251   if (abfd->format != bfd_unknown)
 252     return abfd->format == format;
 253
 254   if (matching != NULL || *bfd_associated_vector != NULL)
 255     {
 256       size_t amt;
 257
 258       amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
 259       matching_vector = (const bfd_target **) bfd_malloc (amt);
 260       if (!matching_vector)
 261         return false;
 262     }
 263
 264   /* Presume the answer is yes.  */
 265   abfd->format = format;
 266   save_targ = abfd->xvec;
 267
 268   preserve_match.marker = NULL;
 269   if (!bfd_preserve_save (abfd, &preserve, NULL))
 270     goto err_ret;
 271
 272   /* If the target type was explicitly specified, just check that target.  */
 273   if (!abfd->target_defaulted)
 274     {
 275       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0) /* rewind! */
 276         goto err_ret;
 277
 278       cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 279
 280       if (cleanup)
 281         goto ok_ret;
 282
 283       /* For a long time the code has dropped through to check all
 284          targets if the specified target was wrong.  I don't know why,
 285          and I'm reluctant to change it.  However, in the case of an
 286          archive, it can cause problems.  If the specified target does
 287          not permit archives (e.g., the binary target), then we should
 288          not allow some other target to recognize it as an archive, but
 289          should instead allow the specified target to recognize it as an
 290          object.  When I first made this change, it broke the PE target,
 291          because the specified pei-i386 target did not recognize the
 292          actual pe-i386 archive.  Since there may be other problems of
 293          this sort, I changed this test to check only for the binary
 294          target.  */
 295       if (format == bfd_archive && save_targ == &binary_vec)
 296         goto err_unrecog;
 297     }
 298
 299   /* Since the target type was defaulted, check them all in the hope
 300      that one will be uniquely recognized.  */
 301   right_targ = NULL;
 302   ar_right_targ = NULL;
 303   match_targ = NULL;
 304   best_match = 256;
 305   best_count = 0;
 306   match_count = 0;
 307   ar_match_index = _bfd_target_vector_entries;
 308
 309   for (target = bfd_target_vector; *target != NULL; target++)
 310     {
 311       void **high_water;
 312
 313       /* The binary target matches anything, so don't return it when
 314          searching.  Don't match the plugin target if we have another
 315          alternative since we want to properly set the input format
 316          before allowing a plugin to claim the file.  Also, don't
 317          check the default target twice.  */
 318       if (*target == &binary_vec
 319 #if BFD_SUPPORTS_PLUGINS
 320           || (match_count != 0 && *target == &plugin_vec)
 321 #endif
 322           || (!abfd->target_defaulted && *target == save_targ))
 323         continue;
 324
 325       /* If we already tried a match, the bfd is modified and may
 326          have sections attached, which will confuse the next
 327          _bfd_check_format call.  */
 328       bfd_reinit (abfd, initial_section_id, cleanup);
 329       /* Free bfd_alloc memory too.  If we have matched and preserved
 330          a target then the high water mark is that much higher.  */
 331       if (preserve_match.marker)
 332         high_water = &preserve_match.marker;
 333       else
 334         high_water = &preserve.marker;
 335       bfd_release (abfd, *high_water);
 336       *high_water = bfd_alloc (abfd, 1);
 337
 338       /* Change BFD's target temporarily.  */
 339       abfd->xvec = *target;
 340
 341       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
 342         goto err_ret;
 343
 344       cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 345       if (cleanup)
 346         {
 347           int match_priority = abfd->xvec->match_priority;
 348 #if BFD_SUPPORTS_PLUGINS
 349           /* If this object can be handled by a plugin, give that the
 350              lowest priority; objects both handled by a plugin and
 351              with an underlying object format will be claimed
 352              separately by the plugin.  */
 353           if (*target == &plugin_vec)
 354             match_priority = (*target)->match_priority;
 355 #endif
 356
 357           if (abfd->format != bfd_archive
 358               || (bfd_has_map (abfd)
 359                   && bfd_get_error () != bfd_error_wrong_object_format))
 360             {
 361               /* If this is the default target, accept it, even if
 362                  other targets might match.  People who want those
 363                  other targets have to set the GNUTARGET variable.  */
 364               if (abfd->xvec == bfd_default_vector[0])
 365                 goto ok_ret;
 366
 367               if (matching_vector)
 368                 matching_vector[match_count] = abfd->xvec;
 369               match_count++;
 370
 371               if (match_priority < best_match)
 372                 {
 373                   best_match = match_priority;
 374                   best_count = 0;
 375                 }
 376               if (match_priority <= best_match)
 377                 {
 378                   /* This format checks out as ok!  */
 379                   right_targ = abfd->xvec;
 380                   best_count++;
 381                 }
 382             }
 383           else
 384             {
 385               /* An archive with no armap or objects of the wrong
 386                  type.  We want this target to match if we get no
 387                  better matches.  */
 388               if (ar_right_targ != bfd_default_vector[0])
 389                 ar_right_targ = *target;
 390               if (matching_vector)
 391                 matching_vector[ar_match_index] = *target;
 392               ar_match_index++;
 393             }
 394
 395           if (preserve_match.marker == NULL)
 396             {
 397               match_targ = abfd->xvec;
 398               if (!bfd_preserve_save (abfd, &preserve_match, cleanup))
 399                 goto err_ret;
 400               cleanup = NULL;
 401             }
 402         }
 403     }
 404
 405   if (best_count == 1)
 406     match_count = 1;
 407
 408   if (match_count == 0)
 409     {
 410       /* Try partial matches.  */
 411       right_targ = ar_right_targ;
 412
 413       if (right_targ == bfd_default_vector[0])
 414         {
 415           match_count = 1;
 416         }
 417       else
 418         {
 419           match_count = ar_match_index - _bfd_target_vector_entries;
 420
 421           if (matching_vector && match_count > 1)
 422             memcpy (matching_vector,
 423                     matching_vector + _bfd_target_vector_entries,
 424                     sizeof (*matching_vector) * match_count);
 425         }
 426     }
 427
 428   /* We have more than one equally good match.  If any of the best
 429      matches is a target in config.bfd targ_defvec or targ_selvecs,
 430      choose it.  */
 431   if (match_count > 1)
 432     {
 433       const bfd_target * const *assoc = bfd_associated_vector;
 434
 435       while ((right_targ = *assoc++) != NULL)
 436         {
 437           int i = match_count;
 438
 439           while (--i >= 0)
 440             if (matching_vector[i] == right_targ
 441                 && right_targ->match_priority <= best_match)
 442               break;
 443
 444           if (i >= 0)
 445             {
 446               match_count = 1;
 447               break;
 448             }
 449         }
 450     }
 451
 452   /* We still have more than one equally good match, and at least some
 453      of the targets support match priority.  Choose the first of the
 454      best matches.  */
 455   if (matching_vector && match_count > 1 && best_count != match_count)
 456     {
 457       int i;
 458
 459       for (i = 0; i < match_count; i++)
 460         {
 461           right_targ = matching_vector[i];
 462           if (right_targ->match_priority <= best_match)
 463             break;
 464         }
 465       match_count = 1;
 466     }
 467
 468   /* There is way too much undoing of half-known state here.  We
 469      really shouldn't iterate on live bfd's.  Note that saving the
 470      whole bfd and restoring it would be even worse; the first thing
 471      you notice is that the cached bfd file position gets out of sync.  */
 472   if (preserve_match.marker != NULL)
 473     cleanup = bfd_preserve_restore (abfd, &preserve_match);
 474
 475   if (match_count == 1)
 476     {
 477       abfd->xvec = right_targ;
 478       /* If we come out of the loop knowing that the last target that
 479          matched is the one we want, then ABFD should still be in a usable
 480          state (except possibly for XVEC).  This is not just an
 481          optimisation.  In the case of plugins a match against the
 482          plugin target can result in the bfd being changed such that
 483          it no longer matches the plugin target, nor will it match
 484          RIGHT_TARG again.  */
 485       if (match_targ != right_targ)
 486         {
 487           bfd_reinit (abfd, initial_section_id, cleanup);
 488           bfd_release (abfd, preserve.marker);
 489           if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
 490             goto err_ret;
 491           cleanup = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 492           BFD_ASSERT (cleanup != NULL);
 493         }
 494
 495     ok_ret:
 496       /* If the file was opened for update, then `output_has_begun'
 497          some time ago when the file was created.  Do not recompute
 498          sections sizes or alignments in _bfd_set_section_contents.
 499          We can not set this flag until after checking the format,
 500          because it will interfere with creation of BFD sections.  */
 501       if (abfd->direction == both_direction)
 502         abfd->output_has_begun = true;
 503
 504       free (matching_vector);
 505       if (preserve_match.marker != NULL)
 506         bfd_preserve_finish (abfd, &preserve_match);
 507       bfd_preserve_finish (abfd, &preserve);
 508
 509       /* File position has moved, BTW.  */
 510       return true;
 511     }
 512
 513   if (match_count == 0)
 514     {
 515     err_unrecog:
 516       bfd_set_error (bfd_error_file_not_recognized);
 517     err_ret:
 518       if (cleanup)
 519         cleanup (abfd);
 520       abfd->xvec = save_targ;
 521       abfd->format = bfd_unknown;
 522       free (matching_vector);
 523       if (preserve_match.marker != NULL)
 524         bfd_preserve_finish (abfd, &preserve_match);
 525       bfd_preserve_restore (abfd, &preserve);
 526       return false;
 527     }
 528
 529   /* Restore original target type and format.  */
 530   abfd->xvec = save_targ;
 531   abfd->format = bfd_unknown;
 532   bfd_set_error (bfd_error_file_ambiguously_recognized);
 533
 534   if (matching)
 535     {
 536       *matching = (char **) matching_vector;
 537       matching_vector[match_count] = NULL;
 538       /* Return target names.  This is a little nasty.  Maybe we
 539          should do another bfd_malloc?  */
 540       while (--match_count >= 0)
 541         {
 542           const char *name = matching_vector[match_count]->name;
 543           *(const char **) &matching_vector[match_count] = name;
 544         }
 545     }
 546   else
 547     free (matching_vector);
 548   if (cleanup)
 549     cleanup (abfd);
 550   if (preserve_match.marker != NULL)
 551     bfd_preserve_finish (abfd, &preserve_match);
 552   bfd_preserve_restore (abfd, &preserve);
 553   return false;
 554 }
 555
 556 /*
 557 FUNCTION
 558         bfd_set_format
 559
 560 SYNOPSIS
 561         bool bfd_set_format (bfd *abfd, bfd_format format);
 562
 563 DESCRIPTION
 564         This function sets the file format of the BFD @var{abfd} to the
 565         format @var{format}. If the target set in the BFD does not
 566         support the format requested, the format is invalid, or the BFD
 567         is not open for writing, then an error occurs.
 568 */
 569
 570 bool
 571 bfd_set_format (bfd *abfd, bfd_format format)
 572 {
 573   if (bfd_read_p (abfd)
 574       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 575     {
 576       bfd_set_error (bfd_error_invalid_operation);
 577       return false;
 578     }
 579
 580   if (abfd->format != bfd_unknown)
 581     return abfd->format == format;
 582
 583   /* Presume the answer is yes.  */
 584   abfd->format = format;
 585
 586   if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
 587     {
 588       abfd->format = bfd_unknown;
 589       return false;
 590     }
 591
 592   return true;
 593 }
 594
 595 /*
 596 FUNCTION
 597         bfd_format_string
 598
 599 SYNOPSIS
 600         const char *bfd_format_string (bfd_format format);
 601
 602 DESCRIPTION
 603         Return a pointer to a const string
 604         <<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
 605         depending upon the value of @var{format}.
 606 */
 607
 608 const char *
 609 bfd_format_string (bfd_format format)
 610 {
 611   if (((int) format < (int) bfd_unknown)
 612       || ((int) format >= (int) bfd_type_end))
 613     return "invalid";
 614
 615   switch (format)
 616     {
 617     case bfd_object:
 618       return "object";          /* Linker/assembler/compiler output.  */
 619     case bfd_archive:
 620       return "archive";         /* Object archive file.  */
 621     case bfd_core:
 622       return "core";            /* Core dump.  */
 623     default:
 624       return "unknown";
 625     }
 626 }